1. Field of the Invention
The present invention relates to a bonded structure and a manufacturing method for the bonded structure that are available for use in a power semiconductor module in which a semiconductor device made of, e.g., SiC (silicon carbide) or GaN (gallium nitride) is bonded to an electrode by a bonding portion.
2. Related Art of the Invention
A material containing Bi (bismuth) or Zn (zinc) is receiving attention as the material for a bonding portion which bonds a semiconductor device to an electrode in a bonded structure of a power semiconductor module that has a higher melting point, is more environmentally-friendly, and is free from Pb (lead).
For example, assume that a Si (silicon) device whose amount of current that can be supplied per unit area is less than 50 mA/cm2 is used as a semiconductor device of a power semiconductor module. In view of ensuring of wettability, ease of bonding, and the like, a material containing 90 wt % or more of Bi is considered to be suitable as the material for a bonding portion bonding the semiconductor device that may rise to about 150° C. to an electrode in this case.
Bi-2.5 wt % Ag (silver) has a melting point of about 262° C. and is a specific example of such a material mainly composed of Bi.
Note that pure Bi, Bi—CuAlMn having CuAlMn (copper, aluminum, and manganese) alloy particles dispersed in Bi, a material in which Cu is added to Bi, and a material in which Ni (nickel) is added to Bi are also known (see, e.g., Japanese Patent Laid-Open No. 2007-281412).
The configuration of a conventional bonded structure 6100 will be described with reference to FIG. 7.
Note that FIG. 7 is a schematic enlarged cross-sectional view of the conventional bonded structure 6100.
A semiconductor device 6110 is bonded to an electrode 6120 by a bonding portion 6130.
A surface-treated layer 6121 is formed on a surface on the bonding portion 6130 side of the electrode 6120.
The bonding portion 6130 is made of the material mainly composed of Bi described above.